O2 sensor placement

[GTP091]

I've long suspected my o2 sensor is causing my car to run rich. It's one of the last sensors i've never replaced; that and the coolant sensors .

 

I just bought and received the magnaflow downpipe and cat for future turbo install. I also ordered 2 weld on SS o2 sensor bungs to add a wideband monitor for a A/F ratio gauge. 1 for the wideband and 1 for the engine management. Is it important to have the O2 sensor close to the manifold to get correct readings? I've always wondered why they seem to be stuck between the firewall and engine where it's nearly impossible to get at them easily on most vehicles. If the factory O2 sensor needs to be close then there it will stay, otherwise it's going farther down the pipe where it's easier to get at.

 

On a side note for those of you who are wise in the ways of engine management what's a good O2 reading on tuner pro for 91 lq1? i just got connected thanks to Robert!

[Andrew]

yes it needs to be close to the engine to work properly. And either of those sensors can cause the engine to run rich.

[GTP091]

Took it for a rip tonight to try some datalogging, couldn't record for some reason (error creating log file). Anyway the engine never came out of closed loop at all. I thought once the engine was warmed up it should switch to open loop? I did see it show open loop very briefly (in red letters) after starting to move after idling for 5 minutes on the side of the road while I was looking at the data. Also shows rich more than lean and the ' slowO2' value flips back and forth from nothing to yes almost like in a rhythm. When it shows yes the rich/lean value shows rich.

 

The O2 sensor values look like a heartbeat under constant speed and jump around under acceleration or idle. drops sharply when let off pedal and coasting down in speed not sure if that's normal or not.

Edited September 7, 2012 by GTP091

[RobertISaar]

sounds like you're using V4, you'll need to create a file to log to first. hit the "select log file for rec/play" button and you'll be able to do so.

 

once the engine warms up, it will go from open loop to closed loop. open loop meaning it ignores a certain sensor(in the case of fueling, the O2 sensor).

 

the value flipping from rich to lean constantly is normal, that's how closed loop operation is maintained with a narrowband sensor.

 

i probably should have relabeled slowO2.... it's essentially a lag filtered fast O2 (the rich/lean flag) value, used for fueling calculations.

 

the way it's reacting sounds normal. what kind of BLM and INT values do you see under a steady load?

 

also, the sensor location is due to two reasons: it's the closest possible location that will allow reading all cylinders instead of just reading one bank. reason #1 for this is it will allow all cylinders to be reported via one sensor. reason #2 is that because it's connected to all cylinders and is in the closest place to do so, it will allow it to heat up faster and allow the ECM to drop into closed loop faster.